"What's next in social media?" It's among the most popular questions out there. But while most folks currently answer with "location-based services" (i.e. Foursquare, Gowalla) or "group purchasing" (i.e. Groupon, Twongo, Living Social), the real battle may be between Facebook and Google.

The fight between these two Internet giants to become your default social profile has been brewing for a long time, and the prize is an enormous potential revenue stream. Let's take a closer look.

Connect It. Buzz It.

Many sites allow you to become a member using Google Friend Connect. While the benefit of doing so wasn't always clear, it was one of the first efforts to encourage the use of Google profiles across the web. Google Buzz and its thus-far poorly executed Gmail integration, is another. Google Wave, if widely adopted and used at its full capability (which hasn't happened yet), would be yet another a compelling reason to use your Google profile as a way to engage with most sites.

At the same time, on many sites, including Mashable, you can use Facebook Connect to leave a comment. If you do, it will grab your profile picture and leave a link to your Facebook profile.

All these features are pretty basic so far, but these are just the recon teams prepping for the coming war. Right now, each company is trying various tactics to condition you to use their service as your default social profile.

Social Commerce is Coming

In April 2009, Forrester released its "Future of the Social Web," a report that outlines five major eras of social media. The final one, set to begin in 2011, is "social commerce," in which social networks start to become intermediaries in the buying process.

With programs like Alvenda, where you can buy flowers from within the Facebook Fan Page of 1-800-Flowers, and Payvment, where you can buy from multiple businesses on Facebook using one shopping cart, we're seeing the early efforts of outsiders to make buying within social networks easy and natural. I believe this will continue. If the process is easy and secure, why wouldn't users feel comfortable making purchases directly through their social interactions with companies and friends? Because of this trend, I expect Facebook and Google to start generating their own revenue streams from these transactions.

In China, the market for virtual goods last year was $5 billion, and the larger social networks in China are profitable — something Facebook is reportedly still reaching toward.

Facebook, therefore, now has a genuine interest in having a very secure, very simple e-commerce platform, where you can buy whatever you want with one-click, similar to Amazon's Kindle Store, and Apple's App Store.

Make Checkout Portable

While Google Checkout has always been designed to be used on other sites, in Q2 this year Facebook will roll out its Open Graph API, which will "allow any page on the web to have all the features of a Facebook Page." If "all the features" includes the ability to make purchases (large or tiny) using Facebook credits, we've got something there. Plus, Facebook just announced that they might automatically connect you with certain pre-approved sites without you even clicking a button — a strong move if their goal is to become that default social profile.

Google can counter this by integrating Checkout data (your credit card, basically) with your Google Profile, allowing sites that choose Google to also have the potential for one-click buying. And both Google and Facebook are good at making these programs easy to implement, so the friction for site owners to add that functionality is very low.

Certainly Amazon has also had a long interest in people using its cart functionality on sites, but I'm not considering it here because it doesn't aim to use your social profile as the hook for connecting - it is a more traditional e-commerce play.

Team Facebook? Team Google?

Suddenly, whether Facebook or Google becomes the default social profile around the web has billion-dollar ramifications. Just ask credit card companies how much can be made by taking just a small percentage of all of those transactions. And with billions at stake, it's likely to be a real battle ahead.

The winners may be all of us, because to compel us to connect using their services, both companies will have to think about providing a lot of genuine utility. When they get creative, we get better web experiences.

Get it right, make it secure, and I'm there.

Which social network do you think will ultimately triumph and why? Share your thoughts in the comments below.

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